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An author alleged to have euthanised his 85-year-old mother shocked friends and family with a book manuscript which detailed how he did it, a court heard yesterday.

A close friend, who has name suppression, told the High Court at Dunedin how he had emailed Sean Davison to warn that he could be charged with murder over the manuscript.

The man was the second of 25 Crown witnesses who will give evidence at the three-week trial of Davison, who is accused of attempting to murder his mother, Dr Patricia Davison (also known as Ferguson), in October 2006 in Dunedin.

The witness said he emailed Davison, a professor at a South African university, after reading the manuscript in early 2008 to say he would be charged with murder, but Davison responded to say his publisher's lawyers had reassured him he should have no concerns on that matter.

The relevant passage was significantly altered in the published book. The witness said it had been well known in the Davison family for many years before she became terminally ill, that Dr Davison did not wish to prolong any serious illness, and would rather die.

The man's evidence was the first of many discussions, emails and other documents stemming from Davison, which the Crown plans to introduce into evidence as it tries to prove to the jury of four men and eight women that Davison administered a lethal dose of methadone to his mother, with the intention of killing her.

The defendant has subsequently become a campaigner for euthanasia legalisation.

Crown solicitor Robin Bates said manuscripts pre-dating the publication of the book consistently referred to the accused administering what he considered to be an overdose to his mother in the hours before her death, with the intention of ending her life.

He said the crucial passage described how his mother's destiny "was not in her hands as she planned, but in mine", how he held the morphine drink to her mouth and she had no difficulty in swallowing, how he could then "only wait and indeed hope" because he knew how devastated his mother would be if she woke up again in the morning.

The published book contained a significantly altered passage.

Defence lawyer Roger Laybourne said this was a very sad case. Davison was a loving and devoted son who took care of his mother during what was a very difficult time. "His defence is simply that he would never attempt to murder his mother, he would never do anything to harm her and would never do anything against her will."

Just because things were said did not necessarily mean they were accurate, Mr Laybourne told the jury.